Motor assisted pedal cycle

ABSTRACT

A motor assisted pedal cycle (30) comprises a pair of pedals (32) connected by crank arms (1,2) to a pedal shaft (3) which is connected to a hub (7) by means of a torsion spring (5). The hub (7) carries a drive sprocket (8) for a chain (36) to connect the hub (7) to the rear wheel of the bicycle. An internal combustion engine (38) is mounted on the bicycle frame and has an output gear for meshing with a drive gear (4) provided on the hub (7). Castellated disks (9,10) are mounted on the pedal shaft (3) and hub (7), respectively, whereby relative displacement of the pedal shaft (3) and hub (7) can be detected by means of an optical sensor (11) provided at the periphery of the disks (9,10). The output of the optical sensor (11) is used to control the engine whereby starting, stopping, and throttle control of the engine is automatically controllable by the force applied to the pedals of the bicycle.

FIELD OF THE INVENTION

This invention relates to a motor assisted pedal cycle and in thepreferred embodiment provides a pedal cycle in which the motor can becontrolled automatically in response to the operation of the pedals.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention a motor assisted pedalcycle comprises: a pair of foot operated rotary pedals for applying adriving torque to a wheel of the cycle; a motor for applying a drivingtorque to a wheel of the cycle; means for sensing the torque reduced byfoot pressure on the pedals as the pedals are rotated to drive thecycle; and control means responsive to the torque sensing means forcontrolling the motor in response to the torque produced by footpressure on the pedals.

With a preferred embodiment of the invention a cycle can be producedhaving a motor, for example an internal combustion engine, which iscontrolled automatically to assist the rider of the cycle in response tothe manner in which the rider of the cycle applies force to the pedalsof the cycle. In a particularly preferred embodiment of the inventionthe throttle opening of an internal combustion engine is increased asthe torque applied to the pedals and/or the speed of rotation of thepedals is increased. In the preferred embodiment, the internalcombustion engine is started automatically when certain predeterminedthreshold conditions are reached, and is stopped automatically inresponse to cessation of pedal rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following detaileddescription of a preferred embodiment thereof, given by way of exampleonly with, reference to the accompanying drawings wherein:

FIG. 1 is a schematic cross-sectional view which illustrates a portionof a bicycle in accordance with the invention;

FIG. 2 illustrates a control box layout; and

FIG. 3 illustrates a control circuit;

FIG. 4 is a schematic elevational view of a typical bicycle with whichthe invention is used.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the invention is in the form of a bicycle 30having a conventional pedal arrangement comprising a pair of pedals (32)connected by crank arms 1 and 2 to a common pedal shaft 3. The pedalshaft is journaled in appropriate bearings mounted on the frame of thebicycle so that the rider of the bicycle may place his feet upon thepedals in the conventional manner. The pedal shaft 3, as described inmore detail hereinafter, applies a drive force to one wheel 34 of thebicycle, e.g. by means of a conventional roller chain arrangement. Amotor, e.g. a small internal combustion engine, is provided to apply adriving torque to one wheel of the bicycle.

Drive from the pedal shaft 3 is applied to the pedal driven wheel of thecycle by means of a sprocket wheel 8 which drives the rear wheel of thebicycle by way of a chain 36. The sprocket wheel 8 is mounted on a hub 7which is rotationally mounted on the frame of the bicycle. A drive gear4 is also mounted on the hub 7 and is engaged by an output gear of aninternal combustion engine 38 mounted on the bicycle frame so that drivefrom the internal combustion engine is transferred to the sprocket 8 bythe gear 4 and hub 7.

The hub 7 is connected to the pedal shaft 3 by means which permitlimited relative angular displacement of the hub relative to the pedalshaft 3. In the illustrated embodiment, a torsion spring 5 is coupled tothe pedal shaft 3 at one end thereof and to a plate 6 at the other endthereof. The plate 6 is connected to the hub 7 which is rotatablysupported on the bicycle frame, and to which the gear 4 and main drivesprocket 8 are connected. The arrangement is such that as the pedals arerotated to drive the sprocket 8 the pedal shaft can advance to a limitedextent relative to the hub 7, the amount of advance being progressive upto a predetermined limit in response to progressively higher torqueapplied to the pedal shaft by foot pressure on the pedals.

A first disk 9 is fast with the pedal shaft 3 and is positioned adjacentto second disk 10 fast with the hub 7. The disks 9,10 have castellatedperipheries as illustrated in FIG. 3, each disk having a multiplicity ofcutaway portions of equal circumferential extent, the cutaway portionsof each disk being separated by lands of circumferential extent equal tothat of the cutaway portion. In the rest position when no torque isapplied to the pedal shaft the torsion spring 5 places the pedal shaft 3and hub 7 in a first predetermined relative position in which the landsof the disk 9 are in register with the cutaway portions of the disk 10,whereby when viewed in a direction parallel to the rotational axis ofthe pedal shaft 3, the disks 9 and 10 together form a solid disk havingno visable slot therein. When force is applied to the pedals, a torqueis applied to the shaft 3 which permits it to advance relative to thehub 7 and moves the slots of the disk 9 progressively into register withthe slots of the disk 10. The connection between the shaft 3 and the hub7 permits only limited relative angular displacement therebetween, andat the maximum available angular displacement the slots of the disk 9are fully in register with the slots of the disk 10. In this position,when viewed in a direction parallel to the axis of the pedal shaft 3 theslots 9,10 appear to have a slotted periphery of equal mark-to-spaceratio.

An optical sensor 11 is positioned to provide an output signal whenevera slot is positioned between the source and the detector of the sensor.Accordingly, as the disks 9,10 rotate in use a pulse output signal isprovided by the optical sensor, the frequency of the pulse is being ameasure of the rotational speed of the disks 9,10 and the mark-to-spaceratio of the pulses being a measure of the degree of register of thedisks 9,10 which in turn is determined by the torque applied to theshaft 3 by pedal pressure.

The output 12 of the sensor is applied to a variable servo amplifier 13to produce an output signal 14 for controlling a servo 15 connected tothe engine throttle. The output of the amplifier 13 is also applied to atrigger circuit 16 which starts the engine in response to apredetermined input from the amplifier 13. The trigger circuit maytypically be arranged to start the engine if the output of the sensor 12achieves a predetermined mark-to-space ratio for a predetermined periodof time. The output 17 of the trigger circuit 16 energizes an ignitionrelay RL2 to turn on the engine ignition and then energizes a starterrelay RL1 to energize the starter motor of the engine. If the output ofthe amplifier 13 falls below the level necessary to trigger the triggercircuit 16 for a predetermined length of time a trigger circuit 18switches off the engine ignition.

In operation, a rider wishing to use the engine assistance pedals thebicycle for a few seconds applying sufficient pedal pressure to producean output necessary to trigger the circuit 16. The engine then starts,and provides assistance in proportion to the force applied to thepedals. By the design of the control circuit, as the rider pedals fasterless pressure is required on the pedals in order the achieve fullthrottle on the engine.

A control box 19 is provided to enable the use of the bicycle to controloperation of the automatic control circuit. The control box 19preferably is provided with a control 20 which varies the operation ofthe servo amplifier to allow the amount of assistance from the engine tobe adjusted. The control box also provides a manual on/off switch 21 forswitching off the engine completely if not required and a"auto/continuous" switch 22 which, when in the CONTINUOUS positionallows the engine to run continuously once started. When the switch 22is in the AUTO position the trigger circuit 18 is able to turn theengine off after a predetermined period of insufficient output from theamplifier 13, as mentioned above.

When the switch 22 is in the CONTINUOUS position the bicycle operatesgenerally in the manner of a conventional moped, but with the enginethrottle control being responsive to pedal pressure rather than manualcontrol. In the AUTO position the engine will only start if the riderexceeds a predetermined pedal pressure for a predetermined period oftime, and thereafter will run continuously under the control of pedalpressure until pedal pressure falls below a predetermined level forsufficiently long to allow the trigger circuit 18 to stop the engine.

Preferably, an "engine on" lamp 23 is provided to show the rider that hehas exceeded the predetermined pedal pressure required to start theengine in the AUTO mode. If the light remains on for more than a fewseconds the rider knows the engine will start and will remain runningfor a predetermined period after the "engine on" lamp has extinguished.

If the rider wishes to prevent the automatic control system fromswitching the engine off whilst he is, for example, stationary attraffic lights without switching the switch 22 to the CONTINUOUS mode,he may apply foot pressure to one of the pedals and gently rock thebicycle backwards and forwards to produce sufficient output from theamplifier 13 to maintain the trigger circuit 16 energized.

Means are preferably provided for adjusting the torque which must beapplied to the pedal shaft in order to achieve maximum throttle. Suchadjustment means may comprise means for adjusting the force of thespring 5, or may consist of an electrical adjustment whereby fullthrottle is achieved before the slots of the disk 9 come fully intoregister with the slots of the disk 10.

In the illustrated embodiment the output 12 of the sensor 11 is fedfirst to an integrator 24 to provide an output voltage 25 proportionalto the mark-to-space ratio of the pulses from the sensor, i.e. an outputvoltage proportional to the force applied to the pedals. By carefuldesign, as the speed of rotation of the pedals is increased and hencethe sensor wave form is generated at a higher frequency the outputvoltage 25 can also be made proportional to the frequency. Thus, whenthe pedals are pressed either at great speed or with high pressure theoutput voltage from the integrator will be high.

The output voltage 25 is then amplified by the amplifier 13 and isaveraged by an appropriate circuit 26 to eliminate fluctuations incontrol voltage as a result of the fact that constant pedal pressurewill not be applied during the whole cycle of rotation of the shaft 3.

When the output of the averager 26 is sufficient to trigger the triggercircuit 16 as described above the output of the trigger circuit isapplied to a delay circuit T1 which, after an appropriate delay, appliesan input 27 to a gate G1. G1 then energizes the starter relay RL1 if noinput 28 is present at the gate G1. As soon as the engine starts engineignition pulses are applied to a trigger circuit 29 in order to producean input 28 at gate G1 to de-energize the relay RL1.

We claim:
 1. An engine assisted pedal cycle comprising: a pair of footoperated rotary pedals for applying a driving torque of varyingmagnitude to a wheel of the cycle; an engine for applying a drivingtorque of varying magnitude to a wheel of the cycle; means for sensingthe magnitude of the torque produced by foot pressure on the pedals asthe pedals are rotated to drive the cycle; and control means responsiveto the torque sensing means for controlling the magnitude of the torqueapplied by the engine in response to the magnitude of the torqueproduced by foot pressure on the pedals.
 2. A pedal cycle as claimed inclaim 1 wherein the torque sensing means comprises: a first diskconnected to the pedals to receive rotary drive therefrom; a second diskcoaxial with the first disk and connected to a wheel of the cycle totransmit drive thereto; coupling means coupling the first disk to thesecond disk in a manner permitting limited relative rotationaldisplacement between said first and second disks, the rotationaldisplacement progressively increasing from zero when no torque isapplied to the pedals to a maximum as torque is progressively applied tothe pedals; and means for sensing the relative displacement of thedisks.
 3. A pedal cycle as claimed in claim 2 and further comprising:frequency sensing means for sensing the frequency of rotation of thepedals, the control means being responsive to the frequency sensingmeans for controlling the engine in response to the frequency ofrotation of the pedals and the magnitude of the torque produced by footpressure on the pedals.
 4. A pedal cycle as claimed in claim 2 wherein:each of said first and second disks is provided with at least onecutaway portion, said at least one cutaway portion of one disk being outof register with a corresponding cutaway portion in the other disk whenno torque is applied to the pedals and being in register with acorresponding cutaway portion in the other disk when the disks are atthe limit of permitted relative rotational displacement; the cutawayportions having an intermediate degree of register as the relativerotational displacement varies between the out of register and inregister positions; and the means for sensing the relative displacementof the disks comprises means for sensing the degree of register betweenthe cutaway portions.
 5. A pedal cycle as claimed in claim 4 wherein:said at least one cutaway portion on each disk comprises a plurality ofsubstantially identical circumferentially extending slots separated bylands having a circumferential extent substantially equal to thecircumferential extent of the slots, the lands of one disk being inregister with the slots of the other disk when no torque is applied tothe pedals and being in register with the lands of the other disk whenthe disks are at the limit of permitted rotational displacement.
 6. Apedal cycle as claimed in claim 5 and further comprising: frequencysensing means for sensing the frequency of rotation of the pedals, thecontrol means being responsive to the frequency sensing means forcontrolling the engine in response to the frequency of rotation of thepedals and the magnitude of the torque produced by foot pressure on thepedals.
 7. A pedal cycle as claimed in claim 6 wherein: the enginecomprises an internal combustion engine; and the control means isoperated to start the engine in response to a predetermined set of pedalmovement characteristics.
 8. A pedal cycle as claimed is claim 7 andfurther comprising: means for overriding the control means to providefor selected starting and operation of the engine.
 9. A pedal cycle asclaimed in claim 7 wherein: the control means is operative to stop theengine in response to one of a cessation of pedal movement and areduction in pedal force below a predetermined limit.
 10. A pedal cycleas claimed in claim 9 and further comprising: means for overriding thecontrol means to provide for selected starting and operation of theengine.
 11. A pedal cycle as claimed in claim 4 and furthercomprising:frequency sensing means for sensing the frequency of rotationof the pedals, the control means being responsive to the frequencysensing means for controlling the engine in response to the frequency ofrotation of the pedals and the magnitude of the torque produced by footpressure on the pedals.
 12. A pedal cycle as claimed in claim 11wherein: the engine comprises an internal combustion engine; and thecontrol means is operated to start the engine in response to apredetermined set of pedal movement characteristics.
 13. A pedal cycleas claimed in claim 12 wherein: the control means is operative to stopthe engine in response to one of a cessation of pedal movement and areduction in pedal force below a predetermined limit.
 14. A pedal cycleas claimed in claim 13 and further comprising:means for overriding thecontrol means to provide for selected starting and operation of theengine.
 15. A pedal cycle as claimed in claim 1 and furthercomprising:frequency sensing means for sensing the frequency of rotationof the pedals, the control means being responsive to the frequencysensing means for controlling the engine in response to the frequency ofrotation of the pedals and the magnitude of the torque produced by footpressure on the pedals.
 16. A pedal cycle as claimed in claim 1 wherein:the engine comprises an internal combustion engine; and the controlmeans is operated to start the engine in response to a predetermined setof pedal movement characteristics.
 17. A pedal cycle as claimed in claim1 wherein: the control means is operative to stop the engine in responseto one of a cessation of pedal movement and a reduction in pedal forcebelow a predetermined limit.